Laminated glass is a type of safety glass that holds together when shattered. An interlayer, typically made of polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA), is included to between two or more layers of glass. The interlayer keeps the layers of glass bonded even when if the glass is broken, and its high strength prevents the glass from breaking up into large sharp pieces. This produces a characteristic “spider web” cracking pattern when the impact is not enough to completely pierce the glass.
Laminated glass is often used when there is a possibility for human impact or where the glass could fall if shattered and also for architectural applications. For example, skylight glazing and automobile windshields typically use laminated glass. In geographical areas requiring hurricane-resistant construction, laminated glass is often used in exterior storefronts, curtain walls, and windows.
Laminated glass is also useful for increasing a sound insulation rating of windows, e.g., it significantly improves sound attenuation compared to monolithic glass panes of the same thickness. For this purpose, a special “acoustic PVB” compound can be used for the interlayer. In the case of the EVA material, no additional acoustic material is required, since the EVA provides sound insulation. An additional benefit for laminated glass for windows is the blockage of ultraviolet radiation by the PVB and EVA interlayer,
A problem with laminated glass is that under high moisture and high temperature conditions, the moisture tends to penetrate openings between glass layers and the interlayer. The moisture disrupts the hydrogen bonding between the interlayer (e.g., PVB sheets) and the glass layers, resulting in delamination of the laminated glass. Therefore, improvements in adhesive properties of the interlayer are needed to avoid delamination.